Frictional holding means



Dec- '31, 1945- J. A. oBERMAn-:R

FRICTIONL HOLDING MEANS File'd Jan. 6, 1944 ff bgg/+5 IN V EN TOR. bhperm'er;

Patented Dec. 31, 1946 UNIT-EDv STATES PATENT OFFICE 2,413,414FRICTIONAL HOLDING MEANS John A. Obermaier, River Forest, Ill.

"Application January 6, 1944, Serial No. 517,255

, Claims.

,1 y This invention relates to adjustable devices, and has to do withmeans for frictionally holding in adjustment an arm or analogousmembermovable about an axis relative to an associated supporting member.

^ VIt is known in electrical measuring instruments,

for example volt meters'and'electrical pyrometers, to provide anadjustable arm for assuringV that the pointer of the instrument will beat the zero mark o-n the dial when the movable coil of the instrument isdeenergized, friction means being provided for holding the arm inadjustment. The friction means commonly used is a known type of springwasher confined under pressure so as to exert pressure on the adjustablearm for holding it in pressure contact with a cooperating surface forholding the arm frictionally in adjustment. That necessitates the use ofan additional part, the spring washer, which involves additionaloperations in assembly and production, and also involves an increase inoverall height of the structure to accommodate the spring washer, all ofwhich contributes to increased co-st and is objectionable for thatreason and, in certain cases, where space is restricted, isVobjectionable as contributing to increased overall height of thestructure. While the frictional holding means of my invention isparticularly suited for use in electrical measuring instruments having amovable coil, and analogous devices, it is also applicable, in itsbroader aspects, to a structure having an arm or analogous memberpivoted for movement between two cooperating supporting members. Inelectric switches, for example, a spring washer of known type commonlyis disposed between the switch blade and an arm of the associatedsupporting clip for holding the blade frictionally in adjustment, whichis objectionable as involving increased operations and increased cost inmaterial, above referred to.

My invention is directed to the provision of frictional holding means ofcomparativelyA simple and inexpensive construction and operation, in

vwhich the necessity for providing an additional part, such as the knowntype of spring washer referred to, is eliminated. More specifically, Iprovide two supporting or mounting members between which an arm oranalogous member is pivoted, one of the mounting members being providedwith resilient fingers cooperating with the arm and the other mountingmember for frictionally holding the arm in adjustment. Further objectsand advantages of my invention will appear from the detail description.

In the drawing:

Figure 1 is a semi-diagrammatic fragmentary plan View of a, known typeof electrical measuring instrument embodying the frictional holdingmeans of my invention;

Figure 2 is a vertical sectional view through the instrument of Figure1, certain parts being shown in elevation, and the instrument casingbeing shown fragmentarily and in section;

FigureB is a plan view of the bridge member of the instrument of Figures1 and 2, on an enlarged scale;v f

Figure 4 is a fragmentary sectional View taken substantially on line 4-4of Figure 3;

Figure 5 is a sectional view taken substantially on. line 5 5 of Figure3, butV showing the adjustable arm and associated parts;

Figure 6 is a-view similar to Figure 3, but showingl a modified form ofbridging member;

Figure 7A is a sectional View taken substantially on line 'I--l ofFigure l;

Figure 8 is a fragmentary side View of a knife switch embodying thefrictional holding means of my invention; and

Figure 9 is a sectional view taken substantially on line 9-9:of Figurey8.

,-In Figures 1, 2 and 5, I have illustrated the frictional holding meansof my invention as applied to an electrical measuring instrument ofknown type, such as a volt meter or an electrical pyrometer. Theseinstruments are well known, and a brief description of the portions ofthe instrument shown will sufce. This instrument comprises pole piecesI0 secured to and extending toward each other from thev pole ends of apermanent magnet (not shown) the opposed faces of the pole pieces I0being provided with arcuate recesses I I which receive a movable coilI2. This coil I2 isv mounted on a suitable frame to which are-securedupper and lower arbors I3 and I II, respectively. The lower arbor I4 ispointed at its lower end and is there mounted, preferably in a jewelbearing, in the upper end`r of a screw I5v threaded through a lowerbridge member I6, formed of copper or other suitable non-magnetic metal,suitably mounted on the pole pieces I 0 and bridging the gaptherebetween. A jam nut I1 is threadedv on screw I5 atthe lower face ofbridge memberlli and cooperates with the latter for locking screw I5 inadjustment. An attaching clip I 8 of substantially L shape is secured onbridge member I 6 and projects upward therefrom, the upwardly extendingarm of clip I8 having secured thereto, by soldering or otherwise, oneend of a torsion spring I9 extending spirally about arbor I4, secured atits other end to the downwardly extending arm of a clip 20 secured toarbor I4, conveniently by being clamped between two nuts 2i screwed onarbor I4, or in any other suitable manner. The upper arbor I3 is pointedat its upper end and is there pivoted in the lower end of a mountingscrew 23, preferably in a jewel bearing member carried by this screw,threaded through an upper bridge member 24. An adjusting arm 25 isconned between the upper face of. bridge member 24 and a nut 25 screwingon the screw 23 and having a hub, as will be explained more fullypresently, contacting bridge member 24 for securing screw 23 inadjustment. Arm 25 is provided, at one end thereoi, with a downwardlyextending nger 21 to which is secured one end of a torsion spring 28wound spirally about arbor I3 in opposite re-A lation for torsion springI9, the other end of torsion spring 28 being secured to the upwardlyextending arm of an L-shaped clip 35 secured on arbor i3. Conveniently,clip 30 is clamped between an upper nut 3l screwing on arbor I3 and anindicator arm 32 mounted on arbor I3 and secured thereto by beingclamped, together with clip 35, between nut 3 lV and a lower nut 33screwed on arbor i3. `The indicator arm or pointer 32 is appropriatelyshaped and disposed to move over a dial4 (not shown) of the instrument,and is provided with a balancing arm 34 weighted in a suitable` manner,as by a drop of solder deposited thereon. It will be understood that theclipsIS and 25., and the clip 30, and the pointer 32 may be mounted andsecured in any suitable known manner other than that disclosed. Arm 25projectsV outward beyond the upper bridge member 24 at the opposite sidethereof from nnger 21, and is provided with an elongated slot 35. Thisslot 36 receives a pin 31 secured in an` adjusting arm 38, at one endthereof, arm 38 being secured at its other end to a nut 39, convenientlyby soldering, which isthreaded on the inner end of va screw 4I passingthrough an opening in top Wall 42 of the instrument casing, there beinga ber washer 43 interposed between arm 33 and wall 42. Nut 39 is fixedto screw 4I in a suitable manner, conveniently by being soldered theretoat 44, armi. 3S being soldered` to nut 349-, as noted, at 45.

The instrument so far described is of known construction and operation,it being understood that the upperA bridge member and the lower bridgemember and parts associated therewith are formed of non-magnetic metal,as is usual. In the known instruments of this character, the adjustablearm 25 is frictionally held in adjustment by the action of a springwasher f known type, above referred to, and adjustment of arm 25Y iseffected by turning'screw 4r in appropriate directions. It willbe notedthat the torsionsprings I9 and 28 act in opposition, with the coil I2-mounted` by needle point bearings for rotation about a vertical'axis,and that the torsion spring 2 8 tends to turn arm 25 about the screw 23.'Ihe frictionof the spring washer, in known instruments, suces to holdarm 25 in adjustment so that, by proper adjustment of arm 25 by means ofscrew 4| and the parts associated therewith, the instrument can beadjusted so that thepointer 32 thereof is at the Zero position of thedial when the coil I2 is deenergized.

The upper bridge member 24 is ofconsiderable thicknessand-is formed ofvspring copper or other` suitable non-magnetic metal; This bridge member24.is mounted adjacenteachend on abrass block 41 provided, at its-lowerend, with a-reduced central hub element 55a.

screw stud 48 threaded into the associated pole piece IU. Block 41 issuitably bored and tapped from its upper end, for reception of asecuring screw 49 passing through bridge member 24 and threading intoblock 41, there being a washer 5B interposed between the head of screw49 and bridge member24. Referring more particularly to Figures l and 3,bridge member 24 is of approximately oblong shape and is provided, atopposite sides of its longitudinal axis, with lengthwise slots 52 fromwhich extend, at the inner ends thereof, outwardly inclined slots 53,providing two pairs of resilient fingers 54 disposed at opposite sidesof the transverse axis of bridge 24, and a central hub element 55 fromwhich extend strips 55, the latter and fingers 54 being integrallyconnected at their outer ends to the bridge 24. The inner ends of thefingers .54 are free from` hub. element 55, those of one pair of thefingers 54 being disposed at the opposite side 0f element 55 to those ofthe other pair of ngers, and the terminalpportions of ngers 54 beingformed at 58 fonsubstantially point contact with an overlying element ofarm 25, as will appear presently. The ngers 54 are deflected upwardrelative to bridge 24, and the free terminal portions thereof are bentupward at an angle, as in Figure 4.

The nut 23 is pro-vided with a reduced inner hub 5.0 seating at itsinner or lower end on hub element 55 of bridge 24,this nut 26 serving asa nut for locking the upper screw 23 in adjustment. Hub 550i nut 2Spasses through hub 5i of the adjustable arm 25, it being noted that hub6G of nut 25 is of slightly greater height than the thickness of hub 6Iof arm 25, providing slight clearance, a few thousandths of an inch,between the upper face of hub element 55 of bridge member 24 andthe-underfaceof hub 5I of arm 2,5, thereby providing slight verticalclearance for hub 6I. When nut 26 is turned tightly onto s:rew 23, theunder face of head 62 thereof, which isiiat and projects radiallyoutward beyond hub 55 a-V considerable extent, overlies hub 6I of arm25, and also overlies-the inner free end portions of resilient ngers 54of bridge member 24. These fingers possess considerable strength andhold hub 5I of arm 25 in pressure contact with the nat under face of theflange of headv 62 of nut 25, eiective'for holding-arm25ml adjustmentabout hub 5,5. Inthat manner, theV resilient fingers 54 of the bridgemember 24` provide means for holding adjustable arm25 inl adjustment, inconjunction with the head1h orrrlange of` nut 23', avoiding necessityfor providing an additional spring element, Vsuch as -arspringwasher ofknown type, and rendering` possible reduction in the overallheight ofthebridge: structure. Itwill be noted that; the fingers `5.4 contact hub 51 of. arm 25 at a plurality of points disposedk diametrically opposite`of hub 5I., vwhich guards against any tendency to tiltingY of this, hub.with possible binding thereof on hub 6.0;of nut 261 Inl'i'gure 6 I haveshown amodiiiedv form of bridge member 24a,A this bridge. member beingprovided with elongated U-'shaped slots 52dy defining resilient lingers5L4aiintegrally connected at their outer ends to the bridge member andwith their inner ends spaced at opposite sides of a rFne fingers 54a aredeflected upwardand havertheir inner terminal portions 58a bent Vupwardat an anglefor contact with the hub BSI.- of arm-25. Inusing-this formof bridge member,4 when the nutlisturned tightly onto screw 23, theresilient-l fingers-54a ana/n4l 5 are forced downwardly and therebyplaced under tension, in the same manner as the fingers 5d of the bridge24 in Figures 1 toll, inclusive, are placed under tension when nut 26 isturned fully onto screw 23. In either case, the spring fingers hold hub6l of adjustable arm 25 in pressure contact with the inner or under faceof the flange of head 62 of nut 26, effective for maintaining arm 25 inadjustment in the manner above def scribed.

In Figures 8 and 9 I have shown a knife switch of known type embodyingthe frictional holding means of my invention. This switch comprises amounting clip 65, bolted or otherwise suitably secured to an insulatingbase B. The clip 65 has two upwardly extending substantially parallelarms 67 and 68 secured together in spaced apart relation by a pivotmember, conveniently a rivet 69, headed at its ends. A switch arm orblade Ill is mounted between arms Gl and 68 on rivet 69 for pivotalmo-vement thereabout. The mounting clip 65 is formed of spring metal ofhigh electrical conductivity, preferably spring copper, and arm E8thereof has struck therefrom a plurality of fingers 'H which aredeflected inwardly so as to bear upon one side of arm l?, the other sideof this arm or blade l!) being in flatwise contact with the inner faceof arm 6i oi' the clip 65 and having a considerable area of contacttherewith. The fingers ll ino-lj switch arm or blade 1E in pressurecontact with arm El of the clip, effective for maintaining blade iii inadjustment about the pivot member or rivet 69. The effective length ofthe rivet 69 is such as to maintain the fingers 'Il under propertension, it being understood that in Figure 9 the distance between thearms 67 and 68 of clips 65 and the inward defiection of the fingers llhave been exaggerated for clearness of illustration. By providing thearm 68 of clip 65 with the resilient lingers 7|, necessity for providinga separate spring washer, as is the present practice. is avoided,effecting a saving in material and saving in time in assembling theswitch structure.

As has been indicated above, and will be understood by those skilled inthis art, changes in construction and arrangement of parts of myinvention may be resorted to without departing from the eld and scopethereof, and I intend to include all such variations, as fall within thescope of the appended claims, in this application in which the preferredforms only of my invention have been disclosed.

I claim:

1. In frictional holding means of the class described, in combination, asupporting member, a second member positioned in closely spaced relationto said supporting member, a pivot member supported by said supportingmember, and an adjustable member mounted between said supporting memberand said second member for turning movement on said pivot member todifferent angular positions, said supporting member being formed ofspring metal and having struck therefrom inwardly deflected resilientfingers bearing on the adjacent face of said adjustable member andholding the opposite face of said adjustable member in pressure contactwith said second member effective to hold said adjustable member inadjustment on said pivot member.

2. In frictional holding means of the class described, in combination, asupporting member, a pivot screw in threaded engagement with saidsupporting member, a nut threaded on said screw into closely spacedrelation to said supporting member, and an adjustable member mountedbetween said supporting member and said nut for turning movement todifferent angular positions aboutL the axis of said screw, saidsupporting member being formed of spring metal and having strucktherefrom inwardly deflected resilient fingers bearing on the adjacentface of said adjustable member and holding the opposite face of saidadjustable member in pressure contact with said nut effective to holdsaid adjustable member in adjustment on said pivot.

3. In frictional holding means of the character described, a fixedbridge member of spring metal, a nut secured to said bridge memberhaving an inner reduced hub and an outer flange projecting radiallyoutward beyond said hub having a flat inner face, and an adjustable armhaving a hub rotatably mounted on the hub of said nut, said bridgemember having integral resilient fingers bearing on the inner face ofthe hub of said arm maintaining the outer face thereof in pressurecontact with the inner face of said. flange effective for holding saidarm frictionally in adjustment about the hub of said nut.

4. In frictional holding means of the character described, e, fixedbridge member of spring metal, a, nut secured to said bridge memberhaving an inner reduced hub and an outer flange projecting radiallyoutward beyond said hub having a fiat inner face, and an adjustable armhaving a hub rotatably mounted on the hub of said nut, said bridgemember having integral resilient fingers bearing on the inner face ofthe hub of said arm at diametrically opposite points thereof maintainingthe outer face of the hub of said arm in pressure contact with the innerface of said flange effective for holding said arm frictionally inadjustment about the hub of said nut.

5. In frictional holding means of the character described, a xed bridgemember of spring metal, Ia nut secured to said bridge member having aninner reduced hub and an outer flange projecting radially outward beyondsaid hub having a at inner face, and an adjustable arm having a hubrotatably mounted on the hub of said nut, the latter hub being ofslightly greater height than the thickness of the hub of said armproviding slight vertical clearance therefor, said bridge member beingslotted thereby providing resilient fingers integral therewith, saidfingers being deflected toward the flange of said nut and bearing on theinner face of the hub of said arm maintaining the outer face thereof inpressure contact with the inner face of said flange effective forholding said arm frictionally in adjustment about the hub of said nut.

6. In frictional holding means of the character described, a fixedbridge member of spring metal, a nut secured to said bridge memberhaving an inner reduced hub and an outer flange projecting radiallyoutward beyond said hub having a fiat inner face, and an adjustable armhaving a hub rotatably mounted on the hub of said nut, the latter hubbeing of slightly greater height than the thickness of the hub of saidarm providing slight vertical clearance therefor, said bridge memberbeing slotted thereby providing resilient fingers integral therewith attheir outer ends and shaped at their inner ends for point contact withthe hub of said arm, said flngers being deflected toward the flange ofsaid nut and bearing on the inner face of the hub of said armmaintaining the outer face thereof in pressure con- 7 tact with theinner face of said iiange effective for holding said arm friction'al-lyin adjustment about the hub of said nut.

'7. In a measuring instrument, a coil pivotedfor rotation about an axis,a fixed bridge member, a screw threaded through said bridge memberproviding a pivot for said coil, a nu'tsthread'ed on said screw lockingit to said bridge member, said nut having an inner reduced hub seat-ingat its inner end on said bridge member and an outer flange projectingradially outward beyond said hub having a flat inner face, an adjustablearm having a hub rotatably mounted o n thev hub off said nut, the latterhub being of slightly greater height than the thickness of the hub ofSaid arm 'providing slight vertical clearance therefor, and a torsionspring anchored at one end to said coil andjat its other end to said armtending to turn the latter about the hub of said nut, said bridge memberbeing formed of spring metal and slotted thereby providing resilientiing'ers integral therewith at their outer endsI and free therefrom attheir inner ends, said iingers being deflected toward the flange of saidnut and bearing on the inner face of the hub of said arm maintaining theouter face thereof in pressure contact with the inner face of saidAflange eiective for holding said arm frictionally in adjustment aboutthe hub of said nut.

8. In a lmeasuring instrument, a coil pivoted for rotation `about anaxis, a fixed lbridgeA `member of spring metal slotted lengthwise atopposite sides of its longitudinal axis -to provide -a Acentral hub andtwo pairs of resilientvr fingers integral with said bridge member "attheir outer ends having their inner ends free ffrom'sa'id bridge memberwith the inner ends of one pair of fingers Adisposed at `one side andythe inner 4ends of the other pair of `iing'ers 'disposed at theVopposite side of the transverse axis of said bridge member, a screwthreaded through said hubproviding a pivot-for said coil. a nutifhreaded on said screw "locking it `to the hub of said bridge member,said nut having-an inner reduced'hub seating-'at its inner 8 end on the'hub of said bridge member and an outer iiange projecting radiallyoutward beyond the hub of said nut having a iiat inner face, anadjustable arm having a hub rotatably mounted on the hub of said nut,the latter hub being of slightly greater height than the thickness ofthe hub of said arm providing slight vertical clearance therefor, and atorsion spring anchored at one end to said coil and at its other end tosaid arm tending to turn-the latter about the hub of said nut, saidfingers being deflected toward the iiange of said nut and bearing on theinner face of the hub of said arm maintaining the outer face thereof inpressure contact with the inner face of said flange effective forholding said arm frictionally in adjustment about the hub of said nut.

9. In frictional holding means of the character described, a mountingclip having two substantially parallel supporting arms, a pivot membersecuring said arms together in spaced relation, and a member mountedbetween said arms on said pivot member for turning movement abo-ut thelatter, said member having a flat surface of appreciable area in Contactwith one of said arms, the other of said arms being formed of springmetal and having struck therefrom inwardly deflected resilient iingersbearing on the opposite face of said member and holding said flatsurface thereof in pressure contact with said one arm eiiective forholding said member frictionally in adjustment about said pivot member.

10. In a devicey of the class described, in cornbination, a pair ofadjacent members, a pivot supported by at least one of said members, andan adjustable member mounted between said adjacent members on said pivotfor turning movement about the axis of the pivot, one of said adjacentmembers being formed of spring metal and having struck therefrominwardly deflected resilient 'fingers adapted to bear on the adjacentface of the adjustable member to hold said adjustable member in angularadjustment.

JOHN A. OBERMAIER.

